etherpad: correct path to node

This was correct on the server but not in ansible. This implies lots of
badness :(
etherpad: bump to 1.3.0 to fix crashes

Hopefully this will kill of a spate of recent crashes of the form

    [2013-12-17 17:49:14.980] [ERROR] console - TypeError: Cannot read property 'colorId' of null
        at /var/www/etherpad-lite/src/node/handler/PadMessageHandler.js:1162:40
        at fn (/var/www/etherpad-lite/src/node_modules/async/lib/async.js:517:34)
        at /var/www/etherpad-lite/src/node_modules/async/lib/async.js:441:34
        at process._tickDomainCallback (node.js:459:13)